Relay actuator circuit



July 20, 1965 c. H. BRUMLEY Y 3,

RELAY ACTUATOR CIRCUIT Original Filed Feb. 18, 1957 United States Patent 3 Claims. (Cl. 317-151) This application is a division of my co-pending application, Serial No. 640,905, filed February 18, 1957, now abandoned, and entitled, Electrical System for a Slide Projector.

Thi invention relates to an improved circuit for actuating an electrical relay, and more particularly to a circuit of this type for actuating a relay in response to an electrical pulse having a relatively small energy content relative to the energy required for full actuation of the relay.

The practice of the invention is broadly applicable in many different fields of use wherever it is desired to actuate an electrical relay in response to a pulse such as a timing pulse, or a current pulse generated by the triggered discharge of a capacitor through the relay winding. The invention was initially developed during the design of an automatic slide projector of the type widely used for projecting images of colored transparencies, or slides upon a screen, and will be described herein in connection with a slide projector of this type.

One important object of the present invention is to provide an improved circuit for actuating a relay in response to a pulse type signal. 7

Other objects are: to provide an improved circuit of this kind including means for maintaining a conditioning current in the relay winding, means for applying a pulse signal to the winding for initiating actuation of the relay, and means responsive to the pulse signal for passing a relatively large holding current through the relay winding,

tion of the relay; to provide an improved circuit of this type which is relatively inexpensive to manufacture, includes only relatively inexpensive components, and is reliable in operation, and long-lasting in service.

These and other objects and advantages of the invention will become apparent in the following description of a representative embodiment thereof taken in conjunction with the drawing wherein:

FIG. 1 is a broken perspective view of a slide projector of the type in which a practical embodiment of the present invention has been incorporated; and

FIG. 2 is a schematic circuit diagram of a circuit according to the invention arranged for controlling automatic and semi-automatic operation of the slide projector shown in FIG. 1.

Briefly, the invention contemplates a circuit for actuating a relay in response to an electrical actuating signal of relatively small energy, and in the illustrated embodiment includes timing means for generating the signal, and a current divider network connected with the relay for establishing a conditioning current through the relay winding preparatory to the actuating signal. The actuating signal is applied directly to the relay winding and is of a magnitude sufiicient to initiate, but in the usual case, not sufficient to complete actuation thereof. The network is arranged to increase the current through the relay winding in response to initial movement of the movable contact of the relay, thereby to complete actuation of the relay and to hold it closed, if desired.

Referring now to the drawing, the slide projector 10 shown therein includes a base platform 12 upon which the various working parts of the projector are supported.

The construction of the slide projector is described in detail, and certain features thereof are claimed in the copending application of Boughton et al., Serial No. 640,710, filed February 18, 1957, now Patent No. 2,949,814 and that patent may be looked to for a complete detailed description of the projector. The present description will be abbreviated, and include only so much detail as is necessary for a clear understanding of the operation of the circuit of the invention.

The projector 10 includes an optical system 18 comprising a projection lens 40 and a projection lamp 32. Means (not separately designated) are provided for condensing the light from the lamp 32 and directing it toward the projection lens 49. Means (not separately designated) are also provided for defining a projection position, and supporting a slide therein between the lamp 32 and condensing system and the lens 40. A slide tray holder 20 is mounted on the base 12 beside the optical system 18 for supporting and guiding a compartmented slide magazine, or tray 52.

A slide transfer arm 22 is supported above the holder 20 and the optical system 18, extending transversely thereacross for smoothly guided reciprocating travel between an advanced position and a retracted position. The transfer arm 22 includes a pair of depending abutments 10 8 and 1119 spaced apart a distance slightly greater than the width of' the slide tray 52 for engaging a slide in one of the compartments of the tray 52 and moving the slide from the tray to the projection position and then returning it to the tray. The advanced position of the transfer arm 22 is its position when the slide is in the projection position, and the retracted position of the transfer arm 22 is its position immediately after it has returned the slide to the tray 52. The transfer arm 22 is shown in its retracted position in FIG. 1.

An electrical motor 94 (not shown in FIG. 1) and a drive mechanism including a level winding screw type cam 63 i arranged for reciprocating the transfer arm 22, and a mechanical linkage (which need not be described herein) is provided for indexing the slide tray 52 in timed relationship to reciprocation of the transfer arm 22. A control panel 24 is secured to the base 12 for mounting various components of the control circuit for controlling the operation of the projector.

The projector is arranged for either automatic or semiautomatic operation, the difference between these two modes being that for semi-automatic operation the timing is manually controlled, whereas for automatic operation the timing is electrically controlled, and once started, the projector will project a full tray of slides in sequence without further attention. In both cases, transfer of the slides from the slide tray compartments into the projection position and their return back to the slide tray compartments is accomplished by reciprocation of the transfer arm 22 from its retracted to its advanced and then back to its retracted position. During operation, that is, during projection of the slides, the transfer arm normally dwells in its advanced position for the time it is desired to display the image upon the screen, and dwells in its retracted position only long enough to permit indexing of the slide tray 52 to bring the next succeeding tray compartment into alignment with the projection position. For loading and unloading purposes, however, that is, when it is desired to insert a new magazine 52, or to index the magazine 52 manually to select a specific slide compartment for showing a slide out of its normal sequence, the transfer arm 22 dwells in its retracted position.

Control of these operations is accomplished by means of the circuit illustrated in FIG. 2, which is connected for controllably actuating the transfer ar drive motor 94. The circuit includes a master ON-OFF switch 216 connected directly in series in one side of the line L1-L2.

A blower motor 160, which is mounted on, the base 12 for cooling the lamp 32, and the lamp 32 are connected for full-time operation while the ON-OFF switch is closed. Control of the transfer motor $4 is effected by a selector switch 162 in conjunction with a limit switch 168. The selector switch 162 is in two electrically so arate sections (not separately designated) each section including three contact points 218, 220, and 222, and 218', 220, and 222', and a contact sector segment 2% and 210, respectively. Connector arms 202 and 204 are separately mounted upon an insulated shaft 266, which is manually rotatable by a knob 196 mounted exteriorly of the control panel 24. When in the position shown in the drawing, the arms 202 and 204 are out of contact with their respective contact points and segments. When the switch is moved to its first position, .the first arm 202 connects the first segment 2% electrically to its first contact 218, and the second arm 204 connects the second segment 210 to its first contact 218. In this first position, the transfer arm 22 is moved to its retracted position, and the motor 94 is stopped when the transfer arm 22 reaches that position. The circuit for this may be traced as follows: one terminal of the motor 94 is connected directly through the master switch 216 to one side L1 of the line. The other terminal of the motor 94 is connected through the first fixed contact 186 of the limit switch 1-68 to the movable arm 188, which in turn is connected to the second fixed contact 182, and through the second movable arm 1% directly to the second side L-2 of the line.

The limit switch 168 isactuated in response to movement of the transfer arm 22 by means of a cam-like dog 170, which is fixed upon a shaft 172 and arranged for moving the first movable contact 188 of the limit switch from its normal position in engagement with the fixed contact 180 into engagement with the third fixed contact 186 when the shaft 172 is rotated in a clockwise direction as viewed in FIG. 2. When the shaft 172 is rotated in the counterclockwise direction, the dog 170 engages the second movable contact 196 of the switch and moves it out of engagement with the second fixed contact 1 82 and into engagement with the fourth fixed contact 192.

Any desired arrangement may be provided for rotating the shaft 172 in response to the arrival of the transfer arm 22 at its advanced and retracted positions. During travel of the arm through the major portion of its path, the shaft 172 and the dog 17ft remain in the intermediate position shown in FIG. 2 so that the movable contacts 188 and 190 of the switch remain in engagement with the first and second fixed contacts 180 and 182, respectively. When the transfer arm reaches its retracted position, the shaft 172 is rotated clockwise to actuate the first movable contact 188. When the transfer arm 22 reaches its advanced position, the dog 17h is moved counterclockwise to actuate the second movable contact 190.

.Now, when the selector switch 162 is moved to its first position, thus connecting the segments 206 and 210 to the respective fixed contacts 218 and 218, the motor 94- will be energized until the transfer arm .22 reaches its retracted position, at which time the motor circuit will be opened at the first fixed contact 180' of the limit switch. The projector is then in condition for receiving a slide tray 52 and for permitting positional adjustment of the slide tray without interference by the transfer arm.

In the next position of the selector switch, in which the segments 206 and 2-10 are connected to their respective contacts 220 and 220', the projector is arranged for semi-automatic operation as controlled through a manualpush button 244 mounted on the control panel 24, or a remote control switch 248 connected in parallel with the panel mounted switch 244.

second terminal of the motor is connected through the fixed contact 229' and the movable arm 204 to the segment 210, which is connected to the second fixed contact 182 of the limit switch, and through this contact 182 and the second movable contact 196 directly to the other side L-2 of the line. The motor 94 will then operate until the second movable contact 1% is moved away from the second fixed contact 182 of the limit switch, which, as hereinabove described, occurs when the transfer arm 22 reaches its advanced position. The motor will then remain de-energized until a by-pass circuit is closed between the second fixed contact 182 and the second side L-2 of the line.

The by-pass circuit is connected through the first fixed contact 263 of a relay 166, the movable contact 27% of which is connected directly to the L-2 side of the line and is normally biased out of engagement with the first fixed contact 268. The fixed contact 182 of the limit switch is connected directly to the. first fixed contact 26% of the relay, so that actuation of the relay connects the second terminal of the motor 94 directly to the L-2 side of the line, by-passing the limit switch 163.

The relay winding 262 is connected to the L2 side of the line in series with a rectifier 252 and various resistors, which will be described hereinafter, through the fourth fixed contact 192 of the limit switch, and when the second movable contact 1% of the limit'switch is actuated into engagement with the fourth fixed contact 1-92, the energizing circuit for the relay winding is completed to the other side L-2 of the line. During the time the transfer arm 22 dwells inits advanced position, current fiows through the relay winding 262, being controlled in amount by the current limiting resistors 25% and 266 to a value just below the value required to actuate the relay. I

The push button 244 and the remote control switch 248 are connected in series with another current limiting resistor 28% for closing a control circuit connecting the resistor 280 in parallel with the first two resistors 25% and 26th, and thus permitting sufiicient additional current to flow through the relay winding 262 to actuate the relay.

The motor then operates to retract the transfer arm, returning the slide to the slide tray compartment, to index the tray, and then to advance the transfer arm 22 again to its advanced position, only stopping when the shaft 172 is rotated counterclockwise, as viewed in PEG. 2 in response to the arrival of the transfer arm 22 at its advanced position. a

A timing circuit, including a capacitor 222 and an electrical trigger device 292 is also included in the circuit for automatic timing, that is, for automatically energizing the relay 166 after a selected dwell time of the transfer arm 22 in its advanced position. This automatic circuit is disabled during semi-automatic operation of'the projector by a direct short circuit across the capacitor 282 through the fixed con-tact 220 of the selector switch, the capacitor 282 beingconnected directly between the fixed contact 220 and the first segment 296. When the selector switch is moved to its third position, the short circuit for the capacitor 282 is opened, and the capacitor 282 is charged exponentially through a fixed resistor 288 and a variable, dwell time adjustment resistor 286 from the direct current supply constituted by the rectifier 252 and the filter resistor 254. and capacitor 3&2.

The timing capacitor 282 is connected in series circuit with the winding 262 of the relay, and the trigger device 292, so that when the voltage across the capacitor exceeds the voltage generated across the relay winding 262 by the conditioning current by the amount required to trip the trigger device 292, the capacitor will discharge through the relay winding to initiate actuation thereof. The trigger device 292 may be of any desired type such as, for example, the gas discharge glow tube illustrated.

The provision of the conditioning current through the relay winding 262, as hereinabove described, provides a bank of stored energy in the magnetic field of the relay winding, thus reducing the amount of energy required from the capacitor 282 to initiate actuation of the relay.

According to the present invention, the power require ment for the timing capacitor 282 is further reduced by an arrangement whereby additional current is supplied to the relay winding 262 in response to initiation of the relay actuation, so that the energy supplied by discharge of the capacitor 2&2 through the relay winding need only be sufiicient to move the movable contact 276 out of engagement wtih the second fixed contact 266, and need not be sufficient to carry the movable contact 270 through its complete travel into engagement with the first fixed contact 268. This is accomplished by a current divider resistor 272, which is connected through the second fixed contact 266 of the relay and the movable contact 27d, in parallel with the second current limiting resistor 260 and the relay winding 262. Normally, during the dwell time of the transfer arm in its advanced position, the conditioning current passing through the first limiting resistor is divided into two paths, part passing through the current divider resistor 272, and part passing through the second limiting resistor 26G) and the relay Winding 262.

When the movable contact 276 of the relay moves out of engagement with the second fixed contact 266, the circuit through the divider resistor 272 is opened, and the current through the second limiting resistor 26%) and the relay winding 262 is consequently increased. The parameters of the circuit, particularly the values of the filter resistor 254, the current limiting resistors 258 and 260, and the current divider resistor 272 are chosen in view of the operating characteristics of the relay 166 so that, (1) when the circuit through the divider resistor 272 is closed, the current through the relay Winding 262 is insuificient to actuate the relay, and (2) when the circuit through the divider 2'72 is opened, the current through the relay winding 262 is sufi'icient to actuate the relay and to hold it closed.

Thus, the timing capacitor 282 may be relatively small, since it need only store sufiicient energy to initiate actuation of the relay 166, actuation of the relay being completed by the action of the current divider network.

Once the relay 166 is actuated, it remains actuated until the circuit through the fourth fixed contact 192 and the second movable contact 199 of the limit switch is broken, that is, until the transfer arm 22 is definitely moved away from its advanced position. The inertia of the motor 94 will carry the transfer arm through the small additional travel required to bring the second movable contact lfiil of the limit switch into engagement with the second fixed contact 182, thereby reestablishing the circuit for the transfer motor 94.

The timing capacitor 282 is also connected to the third fixed contact 186 of the limit switch so that it is discharged completely during the relatively small interval that the transfer arm 22 is in its retracted position. The discharge circuit is a direct short circuit across the timing capacitor 232, and may be traced from the upper side of the capacitor, through the third fixed contact 186 of the limit switch, the first movable contact 188, the second fixed contact 182, and the second movable contact 1%, to the lower side of the capacitor.

What is claimed is:

1. An electrical circuit for actuating a relay of the kind having a winding, a movable contact, first and sec ond fixed contacts, and means normally urging the movable contact into engagement with the first fixed contact, the movable contact being moved out of engagement from the first fixed contact and into engagement with the second fixed contact when the relay is actuated, said circuit comprising, two series connected resistors serially connected to the winding of said relay, a source of direct current voltage connected across said resistors and winding establishing a direct current through the winding in an amount sufficient to actuate the relay, a current shunting resistor connected to the junction of said two series connected resistors and through the normally engaging contacts of said relay to shunt a portion of the current around said winding and limit the current fiow through said winding to a value .insufficient to actuate the relay, means generating a momentary voltage pulse connected across said 5 winding in the same polarity as said source of direct current voltage for applying a voltage pulse of sufiicient magnitude and duration to initiate actuation of the relay and to move the movable contact out of engagement with the first fixed contact and thereby producing a resultant current fiow through the winding to fully actuate said relay.

2. An electrical timing circuit for actuating a relay of the type having a winding, a first and a second fixed contact with a movable contact normally engaging the first of said fixed contacts, said circuit comprising, a source of direct current voltage, a current divider network in cluding a first leg and the winding serially connected across said source of voltage carrying a unidirectional current of sufficient value to actuate said relay, a second leg shunting a portion of said first leg and connected 20 through the normally closed contacts of said relay and shunting a portion of the current normally flowing through said winding to reduce the current fiow in said winding to an amount insufiicient to actuate said relay, a voltage pulse generating means connected across said source of direct current voltage having a triggering device connected at a point intermediate said first leg and said winding producing a voltage pulse across said winding in the same polarity as the source of voltage for initiating actuation of the relay, thereby causing said normally closed contacts to open and divert the flow of current normally through said contacts to flow through said winding and fully actuate said relay.

3. An electrical timing circuit for actuating a relay of the type having an actuating winding, a movable contact, first and second fixed contacts, and means normally urging the movable contact into engagement with the first fixed contact comprising, a current divider network having one leg connected in series with the actuating winding of the relay, a second leg connected through the normally closed contacts in parallel with the Winding, means applying a direct current voltage across said network and relay, said network and relay constructed and arranged in a manner that the relative parameters of said network and said direct current voltage being such that the current flow through said first leg and the winding is sufiicient to actuate the relay when the current of said second leg is open but insuflicient to actuate the relay when the circuit of said second leg is closed, relay actuating means connected across said winding producing a momentary voltage pulse across the winding in the same polarity of the direct current voltage for initiating actuation of the relay, said voltage pulse being of an insufiicient magnitude to fully actuate the relay but sufiicient to cause said normally closed contacts to open and divert the flow of current normally through the second leg of said network through the first leg and said Winding to thereby fully actuate the relay.

References Cited by the Examiner UNITED STATES PATENTS 2,433,254 12/47 Aiken 317151 2,774,015 12/56 White 317128 2,922,086 1/60 Stidger 317--151 FOREIGN PATENTS 623,970 5/49 Great Britain.

SAMUEL BERNSTEIN, Primary Examiner.

LLOYD MCCOLLUM, WALTER L. CARLSON,

Examiners. 

1. AN ELECTRICAL CIRCUIT FOR ACTUATING A RELAY OF THE KIND HAVING A WINDING, A MOVABLE CONTACT, FIRST AND SECOND FIXED CONTACTS, AND MEANS NORMALLY URGING THE MOVABLE CONTACT INTO ENGAGEMENT WITH THE FIRST FIXED CONTACT, THE MOVABLE CONTACT BEING MOVED OUT OF ENGAGEMENT FROM THE FIRST FIXED CONTACT AND INTO ENGAGEMENT WITH THE SECOND FIXED CONTACT WHEN THE RELAY IS ACTUATED, SAID CIRCUIT COMPRISING, TWO SERIES CONNECTED RESISTORS SERIALLY CONNECTED TO THE WINDING OF SAID RELAY, A SOURCE OF DIRECT CURRENT VOLTAGE CONNECTED ACROSS SAID RESISTORS AND WINDING ESTABLISHING A DIRECT CURRENT THROUGH THE WINDING IN AN AMOUNT SUFFICIENT TO ACTUATE THE RELAY, A CURRENT SHUNTING RESISTOR CONNECTED TO THE JUNCTION OF SAID TWO SERIES CONNECTED RESISTORS AND THROUGH THE NORMALLY ENGAGING CONTACTS OF SAID RELAY TO SHUNT A PORTION OF THE CURRENT AROUND SAID WINDING AND LIMIT THE CURRENT FLOW THROUGH SAID WINDING TO A VALUE INSUFFICIENT TO ACTUATE THE RELAY, MEANS GENERATING A MOMENTARY VOLTAGE PULSE CONNECTED ACROSS SAID WINDING IN THE SAME POLARITY AS SAID SOURCE OF DIRECT CURRENT VOLTAGE FOR APPLYING A VOLTAGE PULSE OF SUFFICIENT MAGNITUDE AND DURATION TO INITIATE ACTUATION OF THE RELAY AND TO MOVE THE MOVABLE CONTACT OUT OF ENGAGEMENT WITH THE FIRST FIXED CONTACT AND THEREBY PRODUCING A RESULTANT CURRENT FLOW THROUGH THE WINDING TO FULLY ACTUATE SAID RELAY. 